To meet the requirements of various elements of different voltages in computers these days power supplies generally provide outputs at different voltage levels. For instance a power supply has more than one set of output end for 12V, 5V and 3.3V. Hence the primary power system of the power supply has to branch out necessary auxiliary output circuits from the main circuit. Generation of the auxiliary output circuits mostly relies on a chop-wave circuit. The chop-wave circuit can be seen as a switch circuit with a truncated waveform. It is widely used on a forward transformation circuit that includes a power driving unit, a transformer, a main output unit and at least one auxiliary output unit. The power driving unit delivers electric power through the transformer to the main output unit and auxiliary output unit. The main output unit generates a first sync signal and a second sync signals through a self-excited driving unit to control respectively a main output switch and a main flywheel switch that are ON alternately to deliver output. The chop-wave circuit is used for the secondary side of the transformer to control the level of auxiliary output voltage through ON/OFF of the switches. Reference of the chop-wave circuit is available in R.O.C. patent publication number 186120 entitled “Forward power supply having sync modulation” in which a chop-wave circuit to generate auxiliary output is shown in FIG. 1. In FIG. 1 OUT2 is the output end of the auxiliary output circuit. The chop-wave circuit to control the auxiliary output circuit is controlled by a comparator A. The comparator A has one end capturing the voltage of the secondary side of the transformer 2 (T2) and another end capturing a feedback voltage from an output end of the auxiliary output circuit to the other end. These two are compared by the comparator A, then an output is generated to control ON/OFF of a switch element to alter the electric power output by the auxiliary output circuit. As the comparator has a significant inherent transfer delay, transient action is slow and the response is not desirable. Moreover, the comparator does not have latchup function. Hence in the event that noise interference occurred to one or two input signals at the two ends of the comparator after weighed and balanced erroneous actions are prone to take place and result in control cycle fluctuation. Hence it is relatively not stable. Another reference is depicted in U.S. Pat. No. 6,130,828 entitled “Multiple output converter having self-synchronized pulse width modulation regulation”. It also generates an auxiliary output through a chop-wave circuit. It has an integrator circuit (86) connecting to driver circuit (94). The integrator circuit (86) performs integration of a feedback signal through a capacitor (90) and a resistor (88). The driver circuit (94) has a stop point of ⅓ Vcc and a start point of ⅔ Vcc. The Vcc is the bias voltage power of the driver circuit (94). However, when the capacitor performs integration at ⅔ Vcc a significant transfer delay also occurs. The driver circuit (94) also does not provide latchup function. Moreover, in order to match the driving structure a P type chop-wave switch with a higher impedance and a poorer characteristic has to be used. This causes an additional loss. There are still rooms for improvement to address the undesirable transient response and control cycle fluctuation of the conventional chop circuits.